The present invention relates to a sealing element for a rotary timing system of internal-combustion engines.
Internal-combustion engines are already known in which a rotary timing system replaces the conventional timing system, composed of valves actuated by camshafts.
A type of rotary timing system is disclosed in the U.S. patent application No. 575,640 filed on Jan. 30, 1984 in the name of the same Applicant.
This timing system comprises a hollow distribution cylinder which is divided into internal chambers, two for each cylinder. Each of the chambers has at least two ports and the cylinder rotates synchronously with the crankshaft.
Intermediate sealing elements slide on the distribution cylinder with one of their faces, which is shaped complementarily thereto. The sealing elements are arranged in diametrically opposite rows.
Each of said sealing elements is arranged into holes or ports provided on the engine head and on a body which contains the distribution cylinder, and is composed of a widened cylindrical head which is connected to an also cylindrical body having a smaller cross section.
An axial port crosses each sealing element and, depending on the position of the sealing element, it connects the ports of the disribution cylinder respectively to the induction port of the combustion chamber, to the exhaust port of the chamber, to the induction manifold and with the exhaust manifold.
The body and the head of each sealing element are provided with perimetral grooves for sliding elements which provide a seal on the accommodation seat.
The sealing elements, arranged between the combustion chamber and the distribution cylinder, furthermore require spring members that bias them against the surface of the distribution cylinder.
However, a rotary-cylinder timing system of the type described above has some disadvantages causes mainly by the considerable number of sealing elements, usually four times the number of the cylinders of the engine, and by the consequent constructive complications.
Other disadvantages are due to the high friction which occurs between the large surfaces which are in sliding contact.
The need to arrange at least two sealing elements for each combustion chamber furthermore compromises the possibility of providing large induction and exhaust ports due to the small space available.